Multi-beam metasurface antenna

ABSTRACT

A multibeam antenna and method of using the same are described. In one embodiment, the antenna comprises an aperture having a plurality of radio-frequency (RF) radiating antenna elements. The RF radiating antenna elements generate a plurality of beams simultaneously in different directions in response to a first modulation pattern for holographic beamforming applied to the plurality of RF radiating antenna elements to establish all beams of the plurality of beams such that antenna elements of the plurality of RF radiating antenna elements contribute to all beams in the plurality of beams concurrently. The antenna also includes a controller coupled to the aperture to generate the first modulation pattern.

The present application claims the benefit 35 USC 119(e) of U.S.Provisional Patent Application No. 63/019,151, titled“Multifeed-Multibeam Metasurface Antenna”, filed May 1, 2020 and U.S.Provisional Patent Application No. 63/048,581, titled “Multi-beamMetasurface Antenna”, filed on July 6, 2020, both of which areincorporated by reference in their entirety.

FIELD OF THE INVENTION

Embodiments of the present invention are related to wirelesscommunication; more particularly, embodiments of the present inventionare related to an antenna that generates multiple beams with a singleaperture controlled by one beamforming modulation.

BACKGROUND

Reconfigurable antennas are able to change their properties in a dynamicmatter. These properties typically include frequency, radiation pattern,and polarization properties. One type of reconfigurable antenna is aradio-frequency (RF) metamaterial antenna. Some of these RF metamaterialantennas operate with multiple bands and/or high frequencies, such asthe Ku and Ka frequency bands. One type of metamaterial antenna usesliquid crystal (LC)-based RF radiating metamaterial antenna elements,while another type relies on varactor-based RF radiation elements.

In some current reconfigurable antennas, only a single wireless linkbetween the satellite and the end user can be created. Therefore, ifmultiple wireless links would be desirable at times, such as in the caseof make-before-break situations, these reconfigurable antennas could notprovide two wireless links and the satellite antenna would have tointerrupt an existing wireless link to set up the new wireless link,thereby potentially losing valuable data and/or customer satisfaction.

Some metamaterial antennas have one aperture that generates multiplebeams with their RF radiating antenna elements. In such a case, theantenna creates two beams at two different frequencies and differentantenna elements are used for each of the different beams. Thus, onebeam is generated at one frequency with a portion of the antennaelements of an aperture while another beam is being generated at adifferent frequency with different antenna elements of the aperture.These technologies do not allow for the creation of two beams andchannels operating at the same frequency.

Furthermore, other technologies exist that include apertures that createtwo beams at two different frequencies using multiple feed ports. Thisallows the signals to be kept isolated from each other, and they can beconnected to separate sets of RF chains. However, in these cases, theaperture is used as two terminals that share the same aperture.

SUMMARY

A multibeam antenna and method of using the same are described. In oneembodiment, the antenna comprises an aperture having a plurality ofradio-frequency (RF) radiating antenna elements. The RF radiatingantenna elements generate a plurality of beams simultaneously indifferent directions in response to a first modulation pattern forholographic beamforming applied to the plurality of RF radiating antennaelements to establish all beams of the plurality of beams such thatantenna elements of the plurality of RF radiating antenna elementscontribute to all beams in the plurality of beams concurrently. Theantenna also includes a controller coupled to the aperture to generatethe first modulation pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings. These drawings in no waylimit any changes in form and detail that may be made to the describedembodiments by one skilled in the art without departing from the spiritand scope of the described embodiments.

FIGS. 1A-1C illustrate one embodiment of an antenna with multi-feed,multi-beam configuration.

FIGS. 2A-2C illustrate the radiation patterns of a metasurface antennathat is fed at the same frequency through two ports.

FIGS. 3A-3C illustrate one embodiment of an antenna with a single-feedmulti-beam configuration.

FIG. 3D illustrates an example of the radiation patterns of ametasurface antenna that is fed at the same frequency through a singleport.

FIG. 4A illustrates one embodiment of a flow diagram of a design processfor designing a multibeam antenna with a multi-feed.

FIG. 4B illustrates one embodiment of a flow diagram of a design processfor designing a multibeam antenna with a single feed.

FIG. 4C illustrates one embodiment of a beamforming procedure for amultibeam antenna with a multi-feed.

FIG. 4D illustrates one embodiment of a beamforming procedure for amultibeam antenna with a single feed.

FIGS. 5A-5D illustrate multiple processes for creating a modulation forthe entire aperture to generate multiple beams.

FIG. 5E is a flow diagram of one embodiment of a process for generatingmultiple beams with an antenna aperture.

FIG. 6 illustrates an aperture having one or more arrays of antennaelements placed in concentric rings around an input feed of thecylindrically fed antenna.

FIG. 7 illustrates a perspective view of one row of antenna elementsthat includes a ground plane and a reconfigurable resonator layer.

FIG. 8A illustrates one embodiment of a tunable resonator/slot.

FIG. 8B illustrates a cross section view of one embodiment of a physicalantenna aperture.

FIG. 9A illustrates a portion of the first iris board layer withlocations corresponding to the slots.

FIG. 9B illustrates a portion of the second iris board layer containingslots.

FIG. 9C illustrates patches over a portion of the second iris boardlayer.

FIG. 9D illustrates a top view of a portion of the slotted array.

FIG. 10 illustrates a side view of one embodiment of a cylindrically fedantenna structure.

FIG. 11 illustrates another embodiment of the antenna system with anoutgoing wave.

FIG. 12 illustrates one embodiment of the placement of matrix drivecircuitry with respect to antenna elements.

FIG. 13 illustrates one embodiment of a TFT package.

FIG. 14 is a block diagram of another embodiment of a communicationsystem having simultaneous transmit and receive paths.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providea more thorough explanation of the present invention. It will beapparent, however, to one skilled in the art, that the present inventionmay be practiced without these specific details. In other instances,well-known structures and devices are shown in block diagram form,rather than in detail, in order to avoid obscuring the presentinvention.

An antenna and methods for design of such an antenna are describedherein. In one embodiment, the antenna is a satellite antenna for use ina network terminal of a satellite communication system. In oneembodiment, the antenna is a radial slot antenna. In one embodiment, theantenna is a metasurface antenna having radio-frequency (RF) radiatingantenna elements. In one embodiment, the metasurface antenna is a radialslot antenna. In one embodiment, the RF radiating antenna elements aremetamaterial surface scattering antenna elements. In one embodiment, themetamaterial surface scattering antenna elements are liquid crystal(LC)-based antenna elements. Examples of such antenna elements andantennas are described below. In alternative embodiments, themetamaterial surface scattering antenna elements are antenna elementsthat use a varactor diode or other tuning mechanism as opposed to LCsuch as, for example, those described in U.S. patent application Ser.No. 16/991,924, entitled “Metasurface Antennas Manufactured with MassTransfer Technologies,” filed on Aug. 12, 2020. Note that the techniquescan be used with non-satellite antennas.

In one embodiment, the metasurface antenna has one or more feed portsfor feeding one or more feed waves to the RF radiating antenna elementsand generates two or more reconfigurable radiating beams in response tothese one or more feed waves. In one embodiment, these two or moreradiating beams are independently controlled beams between the antennaand satellites and are spatially separated. That is, the antenna createsmultiple single channels simultaneously that are independent of eachother. Such communication is useful in use cases when creating more thanone reconfigurable link at a time is crucial. In one embodiment, ametasurface antenna disclosed herein can communicate through twoindependent feeds and channels (beam) with two LEO satellites at a timewhere each beam or channel can be reconfigured in real-time based on thelocation and polarization of the satellite with respect to the antenna.For example, communication to a satellite in a LEO constellationrequires that the beam is switched from one satellite to the nextupcoming satellite, and if a multi-beam functionality is not provided,the data will be lost during the transition time. With multipleindependent beams, a new link can be set up before the existing one isinterrupted (make-before-break). In other use cases, operating two beamssimultaneously increases the throughput of the antenna as more data canbe transferred with two or more channels. Thus, this multi-beaminnovation improves the performance of an antenna by creating morecommunication channels that can be used to communicate with multiplesatellites at a time.

In one embodiment, a metasurface antenna with a single feed port can bemodified to possess one or more feed ports and two or more distinctradiation patterns while feed(s) receives from, and/or transmitsthrough, distinct radiation beams in any arbitrary direction andpolarization. In other words, using the techniques described herein, anantenna that is capable of creating only a single reconfigurable beamthat communicates through one feed port can be modified to become anantenna that is able to have more than one reconfigurable beam at a timewhich can communicate through one or several feed ports.

Thus, using the techniques disclosed herein, the problem of having morethan one reconfigurable wireless channel at a time using one antennaunit is solved. In one embodiment, by using a minor hardwaremodification in the current state of an antenna (adding additional feedport in the multi-feed case) and a new beamforming algorithm, an antennacan have with multi-beam capability. This capability can enable anantenna to establish an additional beam and connect to another satellitewhile the first link is maintained.

Examples of Multibeam Antenna Configurations

Multibeam antennas described herein have one of two configurations: amulti-feed, multi-beam antenna configuration and a single-feed,multi-beam antenna configuration. In the multi-feed, multi-beamconfiguration, the antenna creates several independent communicationlinks (transmit/receive) with no additional modifications incommunication channels. In the single-feed multi-beam antenna, theantenna can be also used to establish several transmit channels at atime to transfer data from the antenna to two or more stations. In oneembodiment, the single-feed, multi-beam antenna can be used in thereceive mode for networks where time-division-duplexing is used tocreate communication links. In one embodiment, time division can be usedto create several independent receiving channels through single feed.Any set of orthogonal communication techniques (e.g. spread spectrum,etc.) that can provide a means for separating the received singlesthrough a single feed from two or more spatially separated channels canbe a used for receiving mode when implementing this type of antennaconfiguration.

In one embodiment, the antenna described herein comprises an aperturehaving a plurality of radio-frequency (RF) radiating antenna elements togenerate a plurality of beams simultaneously in different directions.The number of beams may be two or more. In one embodiment, these beamsare generated in response to a modulation pattern for holographicbeamforming applied to the plurality of RF radiating antenna elements toestablish all beams of the plurality of beams such that antenna elementsof the plurality of RF radiating antenna elements contribute to allbeams in the plurality of beams concurrently. A controller coupled tothe aperture generates the modulation pattern that is applied to theantenna elements of the aperture to generate multiple beams.

As set forth above, the antenna can be configured with one or multiplefeeds, or ports (e.g., two ports, three ports, etc.), to provide themultiple beams. In the case of a multi-feed configuration, in oneembodiment, an antenna (e.g., a radial slot antenna) has an aperturethat is fed through two different and independent ports where each portcreates a beam in a specific direction, and those beams are defined by aunique beamforming modulation that satisfies the creation of both beams,namely beam 1 for port 1 and beam 2 for port 2. In other words,beamforming modulation is designed and applied to the antenna elementsof the aperture to create the two beams such that antenna elements ofthe aperture contribute to both beams when ports 1 and 2 are fed withfeed waves. In one embodiment, the beamforming modulation comprises amodulation pattern applied to antenna elements of the antenna apertureto create both beams 1 and 2 when fed by the feed waves from ports 1 and2.

In receive mode, the signal that is received over beam 1 arrivesdominantly at feed port 1 and the beam received over beam 2 arrivesdominantly at port 2. The two beams can be at the same exact frequency.In one embodiment, splitting between the signals occurs through themodulation and the spatial location of the feed ports. In transmit mode,the two beams operate in the same manner as described for the receivemode. Receive and transmit can occur at the same time in the same manneras provided in current antennas for only one beam. Therefore, in oneembodiment, in this configuration, the multi-beam antenna will have twoor more full-duplex beams.

The frequencies of the two beams can be the same or different. Thisapplies to receive and transmit, e.g. the frequency of the receive beamscan be the same while the transmit beams are at the same or differentfrequencies, or vice versa.

FIGS. 1A-1C illustrate one embodiment of an antenna with a multi-feed,multi-beam configuration. Referring to FIGS. 1A-1C, antenna 100 includesan antenna aperture 101 that has antenna elements 102. In oneembodiment, aperture 101 comprises a metasurface and antenna elements102 comprise metamaterial surface scattering antenna elements (e.g.,liquid crystal (LC)-based antenna elements, varactor diode-based antennaelements, etc.). Antenna aperture 101 includes two ports, port 1 andport 2 and generates beam 1 and beam 2.

FIGS. 2A-2C illustrate the radiation patterns of a metasurface antennathat is fed at the same frequency through two ports. A modulationpattern has been applied to establish two beams in the directions ofθ₁=0°, φ₁=45°, LPA₁=35° and θ₂=60°, φ₂=110°, LPA₂=60°, where each ofthem communicates through feed number one and two, respectively.

FIG. 2A illustrates a radiation pattern of the metasurface antenna whenit is fed through port 1 of FIGS. 1A-1C with radiation characteristicsθ₁=0°, φ₁=45°, LPA₁=35°. FIG. 2B illustrates a radiation pattern of themetasurface antenna when it is fed through port 2 with the radiationcharacteristics θ₂=60°, φ₂=110°, LPA₂=60°. FIG. 2C illustrates aradiation pattern of the metasurface antenna when it is fed through bothports simultaneously with radiation characteristics θ₁=0°, φ₁=45°,LPA₁=35° and θ₂=60°, φ₂=110°, LPA₂=60°.

In a single-feed configuration, in one embodiment, a metasurface antennais fed through one port and creates two beams in two differentdirections, and each beam is defined by a unique beamforming modulationthat satisfies the creation of both beam 1 and beam 2 with respect toone port. In other words, beamforming modulation is applied to antennaelements of the antenna aperture to create both beams 1 and 2 when fedby a feed wave from one port. In one embodiment, the beamformingmodulation is in the form of a modulation pattern applied to antennaelements of the antenna aperture.

In the transmit mode, the signal that is transmitted from port 1 will gothrough beam 1 and beam 2. In the receive mode, the signals are receivedfrom each of the two beams at exact same frequency through a singleport. In one embodiment, the splitting between the signals isaccomplished through the time-division-duplexing such that this type ofantenna receives in communication links with specific communicationmodulations..

In one embodiment, in either the multi-feed or single feedconfigurations, the beamforming modulation applied to the antennaelements is able to establish both beams (e.g., beams 1 and 2 of FIGS.1A-1C and FIGS. 3A-3C). In one embodiment, the beamforming modulation isprovided by an antenna controller that generates a beam pattern that issent, or otherwise provided, to the antenna aperture. In one embodiment,the beam pattern is a holographic beam pattern that comprises complexnumbers for each antenna element and the complex number for each elementis selected based on the individual antenna element's contribution toboth beams. In other words, in one embodiment, individual antennaelements are controlled via a complex number from the beamformingmodulation pattern and that number is selected so that the individualantenna elements serves both beams.

FIGS. 3A-3C illustrate one embodiment of an antenna with a single-feedmulti-beam configuration. Referring to FIGS. 3A-3C, antenna 300 includesan antenna aperture 301. Antenna aperture 301 includes antenna elements302. In one embodiment, aperture 301 comprises a metasurface and antennaelements 302 comprise metamaterial surface scattering antenna elements(e.g., liquid crystal (LC)-based antenna elements, varactor diode-basedantenna elements, etc.). Antenna aperture 301 includes a single port,port 303, that generates beam 1 and beam 2.

FIG. 3D illustrates an example of the radiation patterns of ametasurface antenna that is fed at the same frequency through a singleport. Referring to FIG. 3D, a unique modulation pattern has been appliedto establish two beams in the directions (e.g., radiationcharacteristics) of θ₁=0°, φ₁=45°, LPA₁=35° and θ₂=60°, φ₂=110°,LPA₂=60°, where each of them communicates through one feed.

In one embodiment, in either the multi-feed or single feedconfigurations, the beamforming modulation applied to the antennaelements is able to establish both beams (e.g., beams 1 and 2 of FIGS.1A-1C and FIGS. 3A-3C). In one embodiment, the beamforming modulation isprovided by an antenna controller that generates a beam pattern that issent, or otherwise provided, to the antenna aperture. In one embodiment,the beam pattern is a holographic beam pattern that comprises complexnumbers for each antenna element and the complex number for each elementis selected based on the individual antenna element's contribution toboth beams. In other words, in one embodiment, individual antennaelements are controlled via a complex number from the beamformingmodulation pattern and that number is selected so that the individualantenna elements serves both beams.

In the multi-feed configuration, by adding the second port (feed) to theantenna and applying the appropriate beamforming that satisfies thecreation of both beam 1 and beam 2, the antenna can be used to establishtwo independent links to communicate with multiple satellite that arespatially separated. By using the beamforming modulation disclosedherein, a reconfigurable single beam, single feed antenna can betransformed into a multibeam-multi-feed antenna.

In one embodiment, for the single-feed multi-beam configuration, toachieve the multiple beams, specific modulation (beamforming) is appliedon the antenna at the software level and no additional hardwaremodification is required.

Other factors may influence the performance of the multi-feed andsingle-feed configuration disclosed above. By adjusting these aspects ofthe antenna, performance may be improved. The following software andhardware aspects may be adjusted to achieve a certain performance forall beams:

-   -   1) port location, including the location of the ports in the        multi-feed configuration impacts the quality of the isolation        between the beams. From the modulation pattern point of view, if        the spacing between the ports increases, the correlation between        modulation patterns will decrease, and that improves the        isolation between the multiple beams. As an example, in a linear        configuration, the best isolation can be achieved if the ports        are placed at two extremities of the linear array. This concept        can be also extended to an array in a radial configuration.    -   2) density of the antenna elements over the aperture;    -   3) weighting of modulation for each antenna element and every        set of modulations;    -   4) phase of each modulations with respect to each other; and    -   5) phase of the input waves with respect to each other.

FIG. 4A illustrates one embodiment of a flow diagram of a design processfor designing a multibeam antenna with a multi-feed. Referring to FIG.4A, the design process begins by designing the single radiating antennaelement (401), defining the array configuration (e.g., multi-feed, etc.)(402), and designing the metasurface antenna in view of the design ofthe antenna elements and the array configuration (403). The designprocess includes defining the two port locations (404).

With the location of the two ports, the design process continues bydefining the properties of the two beams (405). In one embodiment, theseproperties include the frequency, pointing angle, and polarization foreach of the two beams. Based on these properties, the process definesholographic beamforming modulation to create each beam (406).

Using the holographic beamforming modulation for each beam, the processdefines a unique beamforming modulation based on the two holographicbeamforming modulation (407). In one embodiment, the unique beamformingmodulation is created by combining the two holographic beamformingmodulations. In one embodiment, the combining operation comprises anaveraging operation that averages the modulation patterns for the twoholographic beamforming modulations. The averaging of the modulationpatterns can be done by averaging the complex number for correspondingantenna elements in the two holographic beamforming modulations toarrive at one complex number for that antenna element in the modulationpattern for the unique beamforming modulation. Other ways to generatethe unique beamforming modulation are described in more detail below.Once the unique beamforming modulation has been created, the processsends the unique beamforming modulation (e.g., the beamforming pattern)to the antenna aperture for use in generating the two beams (408).

FIG. 4B illustrates one embodiment of a flow diagram of a design processfor designing a multibeam antenna with a single feed. Referring to FIG.4B, the design process begins by designing the single radiating antennaelement (411), defining the array configuration (e.g., multi-feed, etc.)(412), and designing the metasurface antenna in view of the design ofthe antenna elements and the array configuration (413). The designprocess includes defining a location for the single port (414).

With the location of the port, the design process continues by definingthe properties of the two beams (415). In one embodiment, theseproperties include the frequency, pointing angle, and polarization foreach of the two beams. Based on these properties, the process definesholographic beamforming modulation to create each beam (416).

Using the holographic beamforming modulation for each beam, the processdefines a unique beamforming modulation based on the two holographicbeamforming modulation (417). In one embodiment, the unique beamformingmodulation is created by combining the two holographic beamformingmodulations. In one embodiment, the combining operation comprises anaveraging operation that averages the modulation patterns for the twoholographic beamforming modulations such as described above inconjunction with FIG. 4A or as is described in more detail herein. Oncethe unique beamforming modulation has been created, the process sendsthe unique beamforming modulation (e.g., the beamforming pattern) to theantenna aperture for use in generating the two beams (418).

FIG. 4C illustrates one embodiment of a beamforming process for amultibeam antenna with a multi-feed. The process can be performed byprocessing logic that can include hardware (e.g., circuitry, dedicatedlogic, etc.), software (such as running on a general-purpose computersystem or a dedicated machine), firmware (e.g., software programmed intoa read-only memory), or combinations thereof. In one embodiment, theprocess is performed by an antenna controller that controls the antennaaperture of RF radiating antenna elements.

Referring to FIG. 4C, the process begins by processing logic definingthe holographic beamforming to obtain beams 1-N (processing blocks 420_(1-N)). Next, processing logic calculates the unique beamforming thatcreates beams 1-N when the antenna is fed from ports 1 to N,respectively (processing block 421). In one embodiment, this can be donebased on the best phase approximation, smaller Euclidean distance, oranother mathematical scheme. After calculating the unique beamformingthat creates beams 1-N, processing logic defines the available statesfor beamforming (processing block 422).

FIG. 4D illustrates one embodiment of a beamforming process for amultibeam antenna with a single feed. The process can be performed byprocessing logic that can include hardware (e.g., circuitry, dedicatedlogic, etc.), software (such as running on a general-purpose computersystem or a dedicated machine), firmware (e.g., software programmed intoa read-only memory), or combinations thereof. In one embodiment, theprocess is performed by an antenna controller that controls the antennaaperture of RF radiating antenna elements.

Referring to FIG. 4D, the process begins by processing logic definingthe holographic beamforming to obtain beams 1-N (processing blocks 430_(1-N)). Next, processing logic calculates the unique beamforming thatcreates beams 1-N when the antenna is fed from a single port (processingblock 431). In one embodiment, this can be done based on the best phaseapproximation, smaller Euclidean distance, or another mathematicalscheme. After calculating the unique beamforming that creates beams 1-N,processing logic defines the available states for beamforming(processing block 432).

In one embodiment, in FIGS. 4C and 4D, different weightings are addedfor different holographic modulation and the final modulation is createdbased on weighted holograms that give weight to the creation of eachspecific beam. The equations below summarize modulations with differentweighting where mod is the ideal modulation to create a beam number iwith respect to port i and α_(i) is the weighting of the modulation i.EUC is the Euclidean distance of the ideal modulation from the available(feasible) modulations and γ is the set of available states.

$\begin{matrix}{{Mod_{total}} = \frac{\sum\limits_{i = 1}^{N}\;{a_{i}{mod}_{i}}}{N}} & 1. \\{{{{Mo}d_{total}} = {{argmin}\{ {{EUC}( {\frac{\sum\limits_{i = 1}^{N}\;{a_{i}{mod}_{i}}}{N},\gamma} )} \}}},} & 2.\end{matrix}$

where γ is the set of available states.

-   -   3. Mod_(total)=argmin {Σ_(i=1) ^(N) EUC(α_(i)mod_(i), γ)}, where        γ is the set of available states.    -   4. Mod_(total)={mod₁(elem₁, feed₁); mod₂(elem₂, feed₂); . . . ;        mod_(n)(elem_(n), feed_(n))}    -   5. Any potential modulation pattern based on different        optimization techniques such as, for example, but not limited        to, Genetic algorithm, convex optimizations, particle swarm,        etc. These optimizations are performed on all the RF radiating        elements of the aperture to achieve the desired multi-beam        performance.

For more information on Euclidean modulation, the Euclidean distance,and available states, see U.S. Pat. No. 10,686,636, titled “RestrictedEuclidean Modulation”, and issued Jun. 16, 2020, which is well-known inthe art.

FIGS. 5A-5D illustrate multiple processes for creating a modulation forthe entire aperture to generate multiple beams. These processes areexamples of techniques for deriving the unique beamforming modulation bycombining the individual holographic beamforming modulation for each ofthe beams. Referring to FIGS. 5A-5D, stars 501 and 502 are the idealmodulations to create beam one and two respectively. Solid lines inFIGS. 5A-5D show the minimum Euclidean mapping.

Referring to FIG. 5A, the ideal modulations 501 and 502 are illustratedalong with star 510 that represents the average of the two idealmodulations 501 and 502. In one embodiment, the antenna controller takesthe holographic beamforming patterns for each of the beams and createsthe unique beamforming that is applied to the entire aperture byaveraging corresponding pattern values in the plurality of modulationpatterns for individual RF radiating antenna elements of the pluralityof RF radiating antenna elements. In other words, the modulation patternvalues (e.g., complex numbers) in each modulation pattern for eachelement are averaged and that average value is the modulation patternvalue for that antenna element in the modulation pattern associated withthe unique beamforming modulation that is applied to the entireaperture.

Referring to FIG. 5B, the ideal modulations 501 and 502 are illustratedwith star 510 that represents the average of the two modulations.However, in this case, the antenna controller combines holographicbeamforming patterns for the plurality of beams into one modulationpattern by averaging corresponding pattern values in the modulationpatterns associated with ideal modulations 501 and 502 for individual RFradiating elements of the RF radiating antenna elements and then selectsa Euclidean modulation pattern based on the averaged pattern values asthe modulation pattern for the unique beamforming modulation that isapplied to the entire aperture.

Referring to FIG. 5C, the ideal modulations 501 and 502 are illustrated.To determine the unique beamforming modulation that is applied to theentire aperture, the antenna controller combines holographic beamformingpatterns for the beams by calculating a plurality of Euclideanmodulation mappings for each the holographic beamforming patternsassociated with ideal modulations 501 and 502 for first and secondbeams, generates a plurality of sums by adding patterns for each of theEuclidean modulation mappings for the first beam to patterns for each ofthe corresponding Euclidean modulation mappings for the second beam, andthen selects, as the unique beamforming modulation that is applied tothe entire aperture, the modulation pattern forms the plurality of thesums of the Euclidean modulation mappings having a smallest sum.

In one embodiment, this method is divided in two parts: hardware andsoftware. In the software part, two modulations are calculated to createbeams 1 and 2 from ports 1 and 2, respectively and the appropriateEuclidian mapping is performed to create the feasible modulationpattern. FIG. 5D depicts the proposed modulation scheme. However, on thehardware side, the aperture is composed of elements which are in pairs,and the first modulation to create beam 1 will be applied to the firstset of elements and the second modulation to create beam 2 will beapplied to the second set of elements.

FIG. 5E is a flow diagram of one embodiment of a process for generatingmultiple beams with an antenna aperture having an aperture with aplurality of radio-frequency (RF) radiating antenna elements. Theprocess can be performed by processing logic that can include hardware(e.g., circuitry, dedicated logic, etc.), software (such as is run on ageneral-purpose computer system or a dedicated machine), firmware (e.g.,software programmed into a read-only memory), or combinations thereof.In one embodiment, the process is performed by an antenna controllerthat controls the antenna aperture of RF radiating antenna elements.

Referring to FIG. 5E, the process begins by generating a modulationpattern for each beam of a plurality of beams as a unique holographicbeamforming pattern (processing block 551).

Using the modulation patterns for all the beams, the processing logiccreates a first modulation pattern for holographic beamforming to beapplied to a plurality of RF radiating antenna elements to generate aplurality of beams simultaneously in different directions with allantenna elements of the aperture contributing to all beams in theplurality of beams concurrently (processing block 552). In oneembodiment, the first modulation pattern is a combination of a pluralityof modulation patterns, each modulation pattern in the plurality ofmodulation patterns being for a distinct one of the plurality of beams.

In one embodiment, processing logic creates the first modulation patternby combining the unique holographic beamforming patterns for theplurality of beams into the first modulation pattern. In one embodiment,processing logic combines holographic beamforming patterns for theplurality of beams into the first modulation pattern by averagingcorresponding pattern values in the plurality of modulation patterns forindividual RF radiating elements of the plurality of RF radiatingantenna elements.

In another embodiment, processing logic combines holographic beamformingpatterns for the plurality of beams into the first modulation pattern byapplying different weightings to different holographic beamformingpatterns when combining the unique holographic beamforming patterns intothe first modulation pattern.

In other embodiments, processing logic combines holographic beamformingpatterns for the plurality of beams into the first modulation pattern byone or more of the following:

1) averaging corresponding pattern values in the plurality of modulationpatterns for individual RF radiating elements of the plurality of RFradiating antenna elements, and then selecting a Euclidean modulationpattern based on the one modulation pattern as the first modulationpattern;

2) calculating a plurality of Euclidean modulation mappings for each theholographic beamforming patterns for first and second beams of theplurality of beams, generating a plurality of sums by adding patternsfor each of the Euclidean modulation mappings for the first beam topatterns for each of the corresponding Euclidean modulation mappings forthe second beam, and then selecting, as the unique modulation pattern,the modulation pattern from the plurality of sums of Euclideanmodulation mapping having a smallest sum;

3) calculating two modulations are to create beams 1 and 2 from ports 1and 2, respectively, perform the appropriate Euclidian mapping to createthe feasible modulation pattern, and apply the first modulation tocreate beam 1 to the first set of elements to create beam 1 and thesecond modulation to the second set of elements to create beam 2.

Next, processing logic sends the first modulation pattern to theaperture to cause the plurality of RF radiating antenna elements togenerate a plurality of beams simultaneously (processing block 552).

Note that different weightings can impact antenna performance. Forexample, if one of the beams is given a higher weight, the apertureefficiency and directivity for that beam is higher. If both beams may begiven specific weights to get similar aperture efficiency for bothbeams. These weights may be different.

While the techniques have been described above in conjunction with ametasurface antenna as an active radiator where the feeds have beenincorporated into the antenna, the techniques are not limited to use inthis way. Alternatively, the proposed techniques can also cover thepassive metasurface antennas where the metasurface is simply a reflectorwhile two independent feed antennas (e.g., Horn antennas) areilluminating the metasurface and two different beams are produced.

Examples of Antenna Embodiments

The techniques described above may be used with flat panel antennas.Embodiments of such flat panel antennas are disclosed. The flat panelantennas include one or more arrays of antenna elements on an antennaaperture. In one embodiment, the antenna elements comprise liquidcrystal cells. In one embodiment, the flat panel antenna is acylindrically fed antenna that includes matrix drive circuitry touniquely address and drive each of the antenna elements that are notplaced in rows and columns. In one embodiment, the elements are placedin rings.

In one embodiment, the antenna aperture having the one or more arrays ofantenna elements is comprised of multiple segments coupled together.When coupled together, the combination of the segments form closedconcentric rings of antenna elements. In one embodiment, the concentricrings are concentric with respect to the antenna feed.

Examples of Antenna Systems

In one embodiment, the flat panel antenna is part of a metamaterialantenna system. Embodiments of a metamaterial antenna system forcommunications satellite earth stations are described. In oneembodiment, the antenna system is a component or subsystem of asatellite earth station (ES) operating on a mobile platform (e.g.,aeronautical, maritime, land, etc.) that operates using either Ka-bandfrequencies or Ku-band frequencies for civil commercial satellitecommunications. Note that embodiments of the antenna system also can beused in earth stations that are not on mobile platforms (e.g., fixed ortransportable earth stations).

In one embodiment, the antenna system uses surface scatteringmetamaterial technology to form and steer transmit and receive beamsthrough separate antennas.

In one embodiment, the antenna system is comprised of three functionalsubsystems: (1) a wave guiding structure consisting of a cylindricalwave feed architecture; (2) an array of wave scattering metamaterialunit cells that are part of antenna elements; and (3) a controlstructure to command formation of an adjustable radiation field (beam)from the metamaterial scattering elements using holographic principles.

Antenna Elements

FIG. 6 illustrates the schematic of one embodiment of a cylindricallyfed holographic radial aperture antenna. Referring to FIG. 6, theantenna aperture has one or more arrays 601 of antenna elements 603 thatare placed in concentric rings around an input feed 602 of thecylindrically fed antenna. In one embodiment, antenna elements 603 areradio frequency (RF) resonators that radiate RF energy. In oneembodiment, antenna elements 603 comprise both Rx and Tx irises that areinterleaved and distributed on the whole surface of the antennaaperture. Examples of such antenna elements are described in greaterdetail below. Note that the RF resonators described herein may be usedin antennas that do not include a cylindrical feed.

In one embodiment, the antenna includes a coaxial feed that is used toprovide a cylindrical wave feed via input feed 602. In one embodiment,the cylindrical wave feed architecture feeds the antenna from a centralpoint with an excitation that spreads outward in a cylindrical mannerfrom the feed point. That is, a cylindrically fed antenna creates anoutward travelling concentric feed wave. Even so, the shape of thecylindrical feed antenna around the cylindrical feed can be circular,square or any shape. In another embodiment, a cylindrically fed antennacreates an inward travelling feed wave. In such a case, the feed wavemost naturally comes from a circular structure.

In one embodiment, antenna elements 603 comprise irises and the apertureantenna of FIG. 6 is used to generate a main beam shaped by usingexcitation from a cylindrical feed wave for radiating irises throughtunable liquid crystal (LC) material. In one embodiment, the antenna canbe excited to radiate a horizontally or vertically polarized electricfield at desired scan angles.

In one embodiment, the antenna elements comprise a group of patchantennas. This group of patch antennas comprises an array of scatteringmetamaterial elements. In one embodiment, each scattering element in theantenna system is part of a unit cell that consists of a lowerconductor, a dielectric substrate and an upper conductor that embeds acomplementary electric inductive-capacitive resonator (“complementaryelectric LC” or “CELC”) that is etched in or deposited onto the upperconductor. As would be understood by those skilled in the art, LC in thecontext of CELC refers to inductance-capacitance, as opposed to liquidcrystal.

In one embodiment, a liquid crystal (LC) is disposed in the gap aroundthe scattering element. This LC is driven by the direct driveembodiments described above. In one embodiment, liquid crystal isencapsulated in each unit cell and separates the lower conductorassociated with a slot from an upper conductor associated with itspatch. Liquid crystal has a permittivity that is a function of theorientation of the molecules comprising the liquid crystal, and theorientation of the molecules (and thus the permittivity) can becontrolled by adjusting the bias voltage across the liquid crystal.Using this property, in one embodiment, the liquid crystal integrates anon/off switch for the transmission of energy from the guided wave to theCELC. When switched on, the CELC emits an electromagnetic wave like anelectrically small dipole antenna. Note that the teachings herein arenot limited to having a liquid crystal that operates in a binary fashionwith respect to energy transmission.

In one embodiment, the feed geometry of this antenna system allows theantenna elements to be positioned at forty-five-degree (45° angles tothe vector of the wave in the wave feed. Note that other positions maybe used (e.g., at 40° angles). This position of the elements enablescontrol of the free space wave received by or transmitted/radiated fromthe elements. In one embodiment, the antenna elements are arranged withan inter-element spacing that is less than a free-space wavelength ofthe operating frequency of the antenna. For example, if there are fourscattering elements per wavelength, the elements in the 30 GHz transmitantenna will be approximately 2.5 mm (i.e., ¼th the 10 mm free-spacewavelength of 30 GHz).

In one embodiment, the two sets of elements are perpendicular to eachother and simultaneously have equal amplitude excitation if controlledto the same tuning state. Rotating them +/−45 degrees relative to thefeed wave excitation achieves both desired features at once. Rotatingone set 0 degrees and the other 90 degrees would achieve theperpendicular goal, but not the equal amplitude excitation goal. Notethat 0 and 90 degrees may be used to achieve isolation when feeding thearray of antenna elements in a single structure from two sides.

The amount of radiated power from each unit cell is controlled byapplying a voltage to the patch (potential across the LC channel) usinga controller. Traces to each patch are used to provide the voltage tothe patch antenna. The voltage is used to tune or detune the capacitanceand thus the resonance frequency of individual elements to effectuatebeamforming. The voltage required is dependent on the liquid crystalmixture being used. The voltage tuning characteristic of liquid crystalmixtures is mainly described by a threshold voltage at which the liquidcrystal starts to be affected by the voltage and the saturation voltage,above which an increase of the voltage does not cause major tuning inliquid crystal. These two characteristic parameters can change fordifferent liquid crystal mixtures.

In one embodiment, as discussed above, a matrix drive is used to applyvoltage to the patches in order to drive each cell separately from allthe other cells without having a separate connection for each cell(direct drive). Because of the high density of elements, the matrixdrive is an efficient way to address each cell individually.

In one embodiment, the control structure for the antenna system has 2main components: the antenna array controller, which includes driveelectronics, for the antenna system, is below the wave scatteringstructure, while the matrix drive switching array is interspersedthroughout the radiating RF array in such a way as to not interfere withthe radiation. In one embodiment, the drive electronics for the antennasystem comprise commercial off-the shelf LCD controls used in commercialtelevision appliances that adjust the bias voltage for each scatteringelement by adjusting the amplitude or duty cycle of an AC bias signal tothat element.

In one embodiment, the antenna array controller also contains amicroprocessor executing the software. The control structure may alsoincorporate sensors (e.g., a GPS receiver, a three-axis compass, a3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, etc.) to providelocation and orientation information to the processor. The location andorientation information may be provided to the processor by othersystems in the earth station and/or may not be part of the antennasystem.

More specifically, the antenna array controller controls which elementsare turned off and those elements turned on and at which phase andamplitude level at the frequency of operation. The elements areselectively detuned for frequency operation by voltage application.

For transmission, a controller supplies an array of voltage signals tothe RF patches to create a modulation, or control pattern. The controlpattern causes the elements to be turned to different states. In oneembodiment, multistate control is used in which various elements areturned on and off to varying levels, further approximating a sinusoidalcontrol pattern, as opposed to a square wave (i.e., a sinusoid grayshade modulation pattern). In one embodiment, some elements radiate morestrongly than others, rather than some elements radiate and some do not.Variable radiation is achieved by applying specific voltage levels,which adjusts the liquid crystal permittivity to varying amounts,thereby detuning elements variably and causing some elements to radiatemore than others.

The generation of a focused beam by the metamaterial array of elementscan be explained by the phenomenon of constructive and destructiveinterference. Individual electromagnetic waves sum up (constructiveinterference) if they have the same phase when they meet in free spaceand waves cancel each other (destructive interference) if they are inopposite phase when they meet in free space. If the slots in a slottedantenna are positioned so that each successive slot is positioned at adifferent distance from the excitation point of the guided wave, thescattered wave from that element will have a different phase than thescattered wave of the previous slot. If the slots are spaced one quarterof a guided wavelength apart, each slot will scatter a wave with a onefourth phase delay from the previous slot.

Using the array, the number of patterns of constructive and destructiveinterference that can be produced can be increased so that beams can bepointed theoretically in any direction plus or minus ninety degrees(90°) from the bore sight of the antenna array, using the principles ofholography. Thus, by controlling which metamaterial unit cells areturned on or off (i.e., by changing the pattern of which cells areturned on and which cells are turned off), a different pattern ofconstructive and destructive interference can be produced, and theantenna can change the direction of the main beam. The time required toturn the unit cells on and off dictates the speed at which the beam canbe switched from one location to another location.

In one embodiment, the antenna system produces one steerable beam forthe uplink antenna and one steerable beam for the downlink antenna. Inone embodiment, the antenna system uses metamaterial technology toreceive beams and to decode signals from the satellite and to formtransmit beams that are directed toward the satellite. In oneembodiment, the antenna systems are analog systems, in contrast toantenna systems that employ digital signal processing to electricallyform and steer beams (such as phased array antennas). In one embodiment,the antenna system is considered a “surface” antenna that is planar andrelatively low profile, especially when compared to conventionalsatellite dish receivers.

FIG. 7 illustrates a perspective view of one row of antenna elementsthat includes a ground plane and a reconfigurable resonator layer.Reconfigurable resonator layer 1230 includes an array of tunable slots1210. The array of tunable slots 1210 can be configured to point theantenna in a desired direction. Each of the tunable slots can betuned/adjusted by varying a voltage across the liquid crystal.

Control module 1280 is coupled to reconfigurable resonator layer 1230 tomodulate the array of tunable slots 1210 by varying the voltage acrossthe liquid crystal in FIG. 8A. Control module 1280 may include a FieldProgrammable Gate Array (“FPGA”), a microprocessor, a controller,System-on-a-Chip (SoC), or other processing logic. In one embodiment,control module 1280 includes logic circuitry (e.g., multiplexer) todrive the array of tunable slots 1210. In one embodiment, control module1280 receives data that includes specifications for a holographicdiffraction pattern to be driven onto the array of tunable slots 1210.The holographic diffraction patterns may be generated in response to aspatial relationship between the antenna and a satellite so that theholographic diffraction pattern steers the downlink beams (and uplinkbeam if the antenna system performs transmit) in the appropriatedirection for communication. Although not drawn in each Figure, acontrol module similar to control module 1280 may drive each array oftunable slots described in the Figures of the disclosure.

Radio Frequency (“RF”) holography is also possible using analogoustechniques where a desired RF beam can be generated when an RF referencebeam encounters an RF holographic diffraction pattern. In the case ofsatellite communications, the reference beam is in the form of a feedwave, such as feed wave 1205 (approximately 20 GHz in some embodiments).To transform a feed wave into a radiated beam (either for transmittingor receiving purposes), an interference pattern is calculated betweenthe desired RF beam (the object beam) and the feed wave (the referencebeam). The interference pattern is driven onto the array of tunableslots 1210 as a diffraction pattern so that the feed wave is “steered”into the desired RF beam (having the desired shape and direction). Inother words, the feed wave encountering the holographic diffractionpattern “reconstructs” the object beam, which is formed according todesign requirements of the communication system. The holographicdiffraction pattern contains the excitation of each element and iscalculated by w_(hologram)=w*_(in)w_(out), with w_(in) as the waveequation in the waveguide and w_(out) the wave equation on the outgoingwave.

FIG. 8A illustrates one embodiment of a tunable resonator/slot 1210.Tunable slot 1210 includes an iris/slot 1212, a radiating patch 1211,and liquid crystal 1213 disposed between iris 1212 and patch 1211. Inone embodiment, radiating patch 1211 is co-located with iris 1212.

FIG. 8B illustrates a cross section view of one embodiment of a physicalantenna aperture. The antenna aperture includes ground plane 1245, and ametal layer 1236 within iris layer 1232, which is included inreconfigurable resonator layer 1230. In one embodiment, the antennaaperture of FIG. 8B includes a plurality of tunable resonator/slots 1210of FIG. 8A. Iris/slot 1212 is defined by openings in metal layer 1236. Afeed wave, such as feed wave 1205 of FIG. 7, may have a microwavefrequency compatible with satellite communication channels. The feedwave propagates between ground plane 1245 and resonator layer 1230.

Reconfigurable resonator layer 1230 also includes gasket layer 1233 andpatch layer 1231. Gasket layer 1233 is disposed between patch layer 1231and iris layer 1232. Note that in one embodiment, a spacer could replacegasket layer 1233. In one embodiment, iris layer 1232 is a printedcircuit board (“PCB”) that includes a copper layer as metal layer 1236.In one embodiment, iris layer 1232 is glass. Iris layer 1232 may beother types of substrates.

Openings may be etched in the copper layer to form slots 1212. In oneembodiment, iris layer 1232 is conductively coupled by a conductivebonding layer to another structure (e.g., a waveguide) in FIG. 8B. Notethat in an embodiment the iris layer is not conductively coupled by aconductive bonding layer and is instead interfaced with a non-conductingbonding layer.

Patch layer 1231 may also be a PCB that includes metal as radiatingpatches 1211. In one embodiment, gasket layer 1233 includes spacers 1239that provide a mechanical standoff to define the dimension between metallayer 1236 and patch 1211. In one embodiment, the spacers are 75microns, but other sizes may be used (e.g., 3-200 mm). As mentionedabove, in one embodiment, the antenna aperture of FIG. 8B includesmultiple tunable resonator/slots, such as tunable resonator/slot 1210includes patch 1211, liquid crystal 1213, and iris 1212 of FIG. 8A. Thechamber for liquid crystal 1213A is defined by spacers 1239, iris layer1232 and metal layer 1236. When the chamber is filled with liquidcrystal, patch layer 1231 can be laminated onto spacers 1239 to sealliquid crystal within resonator layer 1230.

A voltage between patch layer 1231 and iris layer 1232 can be modulatedto tune the liquid crystal in the gap between the patch and the slots(e.g., tunable resonator/slot 1210). Adjusting the voltage across liquidcrystal 1213 varies the capacitance of a slot (e.g., tunableresonator/slot 1210). Accordingly, the reactance of a slot (e.g.,tunable resonator/slot 1210) can be varied by changing the capacitance.Resonant frequency of slot 1210 also changes according to the equation

$f = \frac{1}{2\pi\sqrt{LC}}$

where f is the resonant frequency of slot 1210 and L and C are theinductance and capacitance of slot 1210, respectively. The resonantfrequency of slot 1210 affects the energy radiated from feed wave 1205propagating through the waveguide. As an example, if feed wave 1205 is20 GHz, the resonant frequency of a slot 1210 may be adjusted (byvarying the capacitance) to 17 GHz so that the slot 1210 couplessubstantially no energy from feed wave 1205. Or, the resonant frequencyof a slot 1210 may be adjusted to 20 GHz so that the slot 1210 couplesenergy from feed wave 1205 and radiates that energy into free space.Although the examples given are binary (fully radiating or not radiatingat all), full gray scale control of the reactance, and therefore theresonant frequency of slot 1210 is possible with voltage variance over amulti-valued range. Hence, the energy radiated from each slot 1210 canbe finely controlled so that detailed holographic diffraction patternscan be formed by the array of tunable slots.

In one embodiment, tunable slots in a row are spaced from each other byλ/5. Other spacings may be used. In one embodiment, each tunable slot ina row is spaced from the closest tunable slot in an adjacent row by λ/2,and, thus, commonly oriented tunable slots in different rows are spacedby λ/4, though other spacings are possible (e.g., λ/5, λ/6.3). Inanother embodiment, each tunable slot in a row is spaced from theclosest tunable slot in an adjacent row by λ/3.

Embodiments use reconfigurable metamaterial technology, such asdescribed in U.S. patent application Ser. No. 14/550,178, entitled“Dynamic Polarization and Coupling Control from a SteerableCylindrically Fed Holographic Antenna”, filed Nov. 21, 2014 and U.S.patent application Ser. No. 14/610,502, entitled “Ridged Waveguide FeedStructures for Reconfigurable Antenna”, filed Jan. 30, 2015.

FIGS. 9A-D illustrate one embodiment of the different layers forcreating the slotted array. The antenna array includes antenna elementsthat are positioned in rings, such as the example rings shown in FIG. 6.Note that in this example the antenna array has two different types ofantenna elements that are used for two different types of frequencybands.

FIG. 9A illustrates a portion of the first iris board layer withlocations corresponding to the slots. Referring to FIG. 9A, the circlesare open areas/slots in the metallization in the bottom side of the irissubstrate, and are for controlling the coupling of elements to the feed(the feed wave). Note that this layer is an optional layer and is notused in all designs. FIG. 9B illustrates a portion of the second irisboard layer containing slots. FIG. 9C illustrates patches over a portionof the second iris board layer. FIG. 9D illustrates a top view of aportion of the slotted array.

FIG. 10 illustrates a side view of one embodiment of a cylindrically fedantenna structure. The antenna produces an inwardly travelling waveusing a double layer feed structure (i.e., two layers of a feedstructure). In one embodiment, the antenna includes a circular outershape, though this is not required. That is, non-circular inwardtravelling structures can be used. In one embodiment, the antennastructure in FIG. 10 includes a coaxial feed, such as, for example,described in U.S. Publication No. 2015/0236412, entitled “DynamicPolarization and Coupling Control from a Steerable Cylindrically FedHolographic Antenna”, filed on Nov. 21, 2014.

Referring to FIG. 10, a coaxial pin 1601 is used to excite the field onthe lower level of the antenna. In one embodiment, coaxial pin 1601 is a50Ω coax pin that is readily available. Coaxial pin 1601 is coupled(e.g., bolted) to the bottom of the antenna structure, which isconducting ground plane 1602.

Separate from conducting ground plane 1602 is interstitial conductor1603, which is an internal conductor. In one embodiment, conductingground plane 1602 and interstitial conductor 1603 are parallel to eachother. In one embodiment, the distance between ground plane 1602 andinterstitial conductor 1603 is 0.1-0.15″. In another embodiment, thisdistance may be λ/2, where λ is the wavelength of the travelling wave atthe frequency of operation.

Ground plane 1602 is separated from interstitial conductor 1603 via aspacer 1604. In one embodiment, spacer 1604 is a foam or air-likespacer. In one embodiment, spacer 1604 comprises a plastic spacer.

On top of interstitial conductor 1603 is dielectric layer 1605. In oneembodiment, dielectric layer 1605 is plastic. The purpose of dielectriclayer 1605 is to slow the travelling wave relative to free spacevelocity. In one embodiment, dielectric layer 1605 slows the travellingwave by 30% relative to free space. In one embodiment, the range ofindices of refraction that are suitable for beamforming are 1.2-1.8,where free space has by definition an index of refraction equal to 1.Other dielectric spacer materials, such as, for example, plastic, may beused to achieve this effect. Note that materials other than plastic maybe used as long as they achieve the desired wave slowing effect.Alternatively, a material with distributed structures may be used asdielectric 1605, such as periodic sub-wavelength metallic structuresthat can be machined or lithographically defined, for example.

An RF-array 1606 is on top of dielectric 1605. In one embodiment, thedistance between interstitial conductor 1603 and RF-array 1606 is0.1-0.15″. In another embodiment, this distance may be λ_(eff)/2, whereλ_(eff) is the effective wavelength in the medium at the designfrequency.

The antenna includes sides 1607 and 1608. Sides 1607 and 1608 are angledto cause a travelling wave feed from coax pin 1601 to be propagated fromthe area below interstitial conductor 1603 (the spacer layer) to thearea above interstitial conductor 1603 (the dielectric layer) viareflection. In one embodiment, the angle of sides 1607 and 1608 are at45° angles. In an alternative embodiment, sides 1607 and 1608 could bereplaced with a continuous radius to achieve the reflection. While FIG.10 shows angled sides that have angle of 45 degrees, other angles thataccomplish signal transmission from lower-level feed to upper-level feedmay be used. That is, given that the effective wavelength in the lowerfeed will generally be different than in the upper feed, some deviationfrom the ideal 45° angles could be used to aid transmission from thelower to the upper feed level. For example, in another embodiment, the45° angles are replaced with a single step. The steps on one end of theantenna go around the dielectric layer, interstitial the conductor, andthe spacer layer. The same two steps are at the other ends of theselayers.

In operation, when a feed wave is fed in from coaxial pin 1601, the wavetravels outward concentrically oriented from coaxial pin 1601 in thearea between ground plane 1602 and interstitial conductor 1603. Theconcentrically outgoing waves are reflected by sides 1607 and 1608 andtravel inwardly in the area between interstitial conductor 1603 and RFarray 1606. The reflection from the edge of the circular perimetercauses the wave to remain in phase (i.e., it is an in-phase reflection).The travelling wave is slowed by dielectric layer 1605. At this point,the travelling wave starts interacting and exciting with elements in RFarray 1606 to obtain the desired scattering.

To terminate the travelling wave, a termination 1609 is included in theantenna at the geometric center of the antenna. In one embodiment,termination 1609 comprises a pin termination (e.g., a 50Ω pin). Inanother embodiment, termination 1609 comprises an RF absorber thatterminates unused energy to prevent reflections of that unused energyback through the feed structure of the antenna. These could be used atthe top of RF array 1606.

FIG. 11 illustrates another embodiment of the antenna system with anoutgoing wave. Referring to FIG. 11, two ground planes 1610 and 1611 aresubstantially parallel to each other with a dielectric layer 1612 (e.g.,a plastic layer, etc.) in between ground planes. RF absorbers 1619(e.g., resistors) couple the two ground planes 1610 and 1611 together. Acoaxial pin 1615 (e.g., 50Ω) feeds the antenna. An RF array 1616 is ontop of dielectric layer 1612 and ground plane 1611.

In operation, a feed wave is fed through coaxial pin 1615 and travelsconcentrically outward and interacts with the elements of RF array 1616.

The cylindrical feed in both the antennas of FIGS. 10 and 11 improvesthe service angle of the antenna. Instead of a service angle of plus orminus forty-five degrees azimuth (±45° Az) and plus or minus twenty-fivedegrees elevation (±25° El), in one embodiment, the antenna system has aservice angle of seventy-five degrees (75°) from the bore sight in alldirections. As with any beamforming antenna comprised of many individualradiators, the overall antenna gain is dependent on the gain of theconstituent elements, which themselves are angle-dependent. When usingcommon radiating elements, the overall antenna gain typically decreasesas the beam is pointed further off bore sight. At 75 degrees off boresight, significant gain degradation of about 6 dB is expected.

Embodiments of the antenna having a cylindrical feed solve one or moreproblems. These include dramatically simplifying the feed structurecompared to antennas fed with a corporate divider network and thereforereducing total required antenna and antenna feed volume; decreasingsensitivity to manufacturing and control errors by maintaining high beamperformance with coarser controls (extending all the way to simplebinary control); giving a more advantageous side lobe pattern comparedto rectilinear feeds because the cylindrically oriented feed wavesresult in spatially diverse side lobes in the far field; and allowingpolarization to be dynamic, including allowing left-hand circular,right-hand circular, and linear polarizations, while not requiring apolarizer.

Array of Wave Scattering Elements

RF array 1606 of FIG. 10 and RF array 1616 of FIG. 11 include a wavescattering subsystem that includes a group of patch antennas (i.e.,scatterers) that act as radiators. This group of patch antennascomprises an array of scattering metamaterial elements.

In one embodiment, each scattering element in the antenna system is partof a unit cell that consists of a lower conductor, a dielectricsubstrate and an upper conductor that embeds a complementary electricinductive-capacitive resonator (“complementary electric LC” or “CELC”)that is etched in or deposited onto the upper conductor.

In one embodiment, a liquid crystal (LC) is injected in the gap aroundthe scattering element. Liquid crystal is encapsulated in each unit celland separates the lower conductor associated with a slot from an upperconductor associated with its patch. Liquid crystal has a permittivitythat is a function of the orientation of the molecules comprising theliquid crystal, and the orientation of the molecules (and thus thepermittivity) can be controlled by adjusting the bias voltage across theliquid crystal. Using this property, the liquid crystal acts as anon/off switch for the transmission of energy from the guided wave to theCELC. When switched on, the CELC emits an electromagnetic wave like anelectrically small dipole antenna.

Controlling the thickness of the LC increases the beam switching speed.A fifty percent (50%) reduction in the gap between the lower and theupper conductor (the thickness of the liquid crystal) results in afourfold increase in speed. In another embodiment, the thickness of theliquid crystal results in a beam switching speed of approximatelyfourteen milliseconds (14 ms). In one embodiment, the LC is doped in amanner well-known in the art to improve responsiveness so that a sevenmillisecond (7 ms) requirement can be met.

The CELC element is responsive to a magnetic field that is appliedparallel to the plane of the CELC element and perpendicular to the CELCgap complement. When a voltage is applied to the liquid crystal in themetamaterial scattering unit cell, the magnetic field component of theguided wave induces a magnetic excitation of the CELC, which, in turn,produces an electromagnetic wave in the same frequency as the guidedwave.

The phase of the electromagnetic wave generated by a single CELC can beselected by the position of the CELC on the vector of the guided wave.Each cell generates a wave in phase with the guided wave parallel to theCELC. Because the CELCs are smaller than the wave length, the outputwave has the same phase as the phase of the guided wave as it passesbeneath the CELC.

In one embodiment, the cylindrical feed geometry of this antenna systemallows the CELC elements to be positioned at forty-five-degree (45°)angles to the vector of the wave in the wave feed. This position of theelements enables control of the polarization of the free space wavegenerated from or received by the elements. In one embodiment, the CELCsare arranged with an inter-element spacing that is less than afree-space wavelength of the operating frequency of the antenna. Forexample, if there are four scattering elements per wavelength, theelements in the 30 GHz transmit antenna will be approximately 2.5 mm(i.e., ¼th the 10 mm free-space wavelength of 30 GHz).

In one embodiment, the CELCs are implemented with patch antennas thatinclude a patch co-located over a slot with liquid crystal between thetwo. In this respect, the metamaterial antenna acts like a slotted(scattering) wave guide. With a slotted wave guide, the phase of theoutput wave depends on the location of the slot in relation to theguided wave.

Cell Placement

In one embodiment, the antenna elements are placed on the cylindricalfeed antenna aperture in a way that allows for a systematic matrix drivecircuit. The placement of the cells includes placement of thetransistors for the matrix drive. FIG. 12 illustrates one embodiment ofthe placement of matrix drive circuitry with respect to antennaelements. Referring to FIG. 12, row controller 1701 is coupled totransistors 1711 and 1712, via row select signals Row1 and Row2,respectively, and column controller 1702 is coupled to transistors 1711and 1712 via column select signal Column1. Transistor 1711 is alsocoupled to antenna element 1721 via connection to patch 1731, whiletransistor 1712 is coupled to antenna element 1722 via connection topatch 1732.

In an initial approach to realize matrix drive circuitry on thecylindrical feed antenna with unit cells placed in a non-regular grid,two steps are performed. In the first step, the cells are placed onconcentric rings and each of the cells is connected to a transistor thatis placed beside the cell and acts as a switch to drive each cellseparately. In the second step, the matrix drive circuitry is built inorder to connect every transistor with a unique address as the matrixdrive approach requires. Because the matrix drive circuit is built byrow and column traces (similar to LCDs) but the cells are placed onrings, there is no systematic way to assign a unique address to eachtransistor. This mapping problem results in very complex circuitry tocover all the transistors and leads to a significant increase in thenumber of physical traces to accomplish the routing. Because of the highdensity of cells, those traces disturb the RF performance of the antennadue to coupling effect. Also, due to the complexity of traces and highpacking density, the routing of the traces cannot be accomplished bycommercially available layout tools.

In one embodiment, the matrix drive circuitry is predefined before thecells and transistors are placed. This ensures a minimum number oftraces that are necessary to drive all the cells, each with a uniqueaddress. This strategy reduces the complexity of the drive circuitry andsimplifies the routing, which subsequently improves the RF performanceof the antenna.

More specifically, in one approach, in the first step, the cells areplaced on a regular rectangular grid composed of rows and columns thatdescribe the unique address of each cell. In the second step, the cellsare grouped and transformed to concentric circles while maintainingtheir address and connection to the rows and columns as defined in thefirst step. A goal of this transformation is not only to put the cellson rings but also to keep the distance between cells and the distancebetween rings constant over the entire aperture. In order to accomplishthis goal, there are several ways to group the cells.

In one embodiment, a TFT package is used to enable placement and uniqueaddressing in the matrix drive. FIG. 13 illustrates one embodiment of aTFT package. Referring to FIG. 13, a TFT and a hold capacitor 1803 isshown with input and output ports. There are two input ports connectedto traces 1801 and two output ports connected to traces 1802 to connectthe TFTs together using the rows and columns. In one embodiment, the rowand column traces cross in 90° angles to reduce, and potentiallyminimize, the coupling between the row and column traces. In oneembodiment, the row and column traces are on different layers.

An Example of a Full Duplex Communication System

In another embodiment, the combined antenna apertures are used in a fullduplex communication system. FIG. 14 is a block diagram of anotherembodiment of a communication system having simultaneous transmit andreceive paths. While only one transmit path and one receive path areshown, the communication system may include more than one transmit pathand/or more than one receive path.

Referring to FIG. 14, antenna 1401 includes two spatially interleavedantenna arrays operable independently to transmit and receivesimultaneously at different frequencies as described above. In oneembodiment, antenna 1401 is coupled to diplexer 1445. The coupling maybe by one or more feeding networks. In one embodiment, in the case of aradial feed antenna, diplexer 1445 combines the two signals and theconnection between antenna 1401 and diplexer 1445 is a single broad-bandfeeding network that can carry both frequencies.

Diplexer 1445 is coupled to a low noise block down converter (LNB) 1427,which performs a noise filtering function and a down conversion andamplification function in a manner well-known in the art. In oneembodiment, LNB 1427 is in an out-door unit (ODU). In anotherembodiment, LNB 1427 is integrated into the antenna apparatus. LNB 1427is coupled to a modem 1460, which is coupled to computing system 1440(e.g., a computer system, modem, etc.).

Modem 1460 includes an analog-to-digital converter (ADC) 1422, which iscoupled to LNB 1427, to convert the received signal output from diplexer1445 into digital format. Once converted to digital format, the signalis demodulated by demodulator 1423 and decoded by decoder 1424 to obtainthe encoded data on the received wave. The decoded data is then sent tocontroller 1425, which sends it to computing system 1440.

Modem 1460 also includes an encoder 1430 that encodes data to betransmitted from computing system 1440. The encoded data is modulated bymodulator 1431 and then converted to analog by digital-to-analogconverter (DAC) 1432. The analog signal is then filtered by a BUC(up-convert and high pass amplifier) 1433 and provided to one port ofdiplexer 1445. In one embodiment, BUC 1433 is in an out-door unit (ODU).

Diplexer 1445 operating in a manner well-known in the art provides thetransmit signal to antenna 1401 for transmission.

Controller 1450 controls antenna 1401, including the two arrays ofantenna elements on the single combined physical aperture.

The communication system would be modified to include thecombiner/arbiter described above. In such a case, the combiner/arbiterafter the modem but before the BUC and LNB.

Note that the full duplex communication system shown in FIG. 14 has anumber of applications, including but not limited to, internetcommunication, vehicle communication (including software updating), etc.

There is a number of example embodiments described herein.

Example 1 is an antenna comprising: an aperture having a plurality ofradio-frequency (RF) radiating antenna elements to generate a pluralityof beams simultaneously in different directions in response to a firstmodulation pattern for beamforming applied to the plurality of RFradiating antenna elements to establish all beams of the plurality ofbeams such that antenna elements of the plurality of RF radiatingantenna elements contribute to all beams in the plurality of beamsconcurrently; and a controller coupled to the aperture to generate thefirst modulation pattern.

Example 2 is the antenna of example 1 that may optionally include thatthe first modulation pattern is a combination of a plurality ofmodulation patterns, each modulation pattern in the plurality ofmodulation patterns being for a distinct one of the plurality of beams.

Example 3 is the antenna of example 2 that may optionally include thatthe controller is operable to generate each modulation pattern for eachbeam of the plurality of beams as a separate beamforming pattern,combine the separate holographic beamforming patterns for the pluralityof beams into the first modulation pattern, and send the firstmodulation pattern to the aperture.

Example 4 is the antenna of example 3 that may optionally include thatthe controller is operable combine beamforming patterns for theplurality of beams into the first modulation pattern by averagingcorresponding pattern values in the plurality of modulation patterns forindividual RF radiating elements of the plurality of RF radiatingantenna elements.

Example 5 is the antenna of example 3 that may optionally include thatthe controller is operable to combine beamforming patterns for theplurality of beams into one modulation pattern by: averagingcorresponding pattern values in the plurality of modulation patterns forindividual RF radiating elements of the plurality of RF radiatingantenna elements, and then selecting a Euclidean modulation patternbased on the one modulation pattern as the first modulation pattern.

Example 6 is the antenna of example 3 that may optionally include thatthe controller is operable combine beamforming patterns for theplurality of beams into the first modulation pattern by: calculating aplurality of Euclidean modulation mappings for each the beamformingpatterns for first and second beams of the plurality of beams;generating a plurality of sums by adding patterns for each of theEuclidean modulation mappings for first beam to patterns for each of thecorresponding Euclidean modulation mappings for the second beam, andthen selecting, as the first modulation pattern, the Euclideanmodulation pattern for the Euclidean modulation mapping having asmallest sum from the plurality of sums.

Example 7 is the antenna of example 3 that may optionally include thatthe controller is operable combine beamforming patterns for theplurality of beams into the first modulation pattern by: selecting aEuclidean modulation pattern associated with a closest Euclideanmodulation mapping for each of the beamforming patterns for theplurality of beams; and averaging the Euclidean modulation patterns forthe closest Euclidean modulation mappings for the plurality of thebeamforming patterns.

Example 8 is the antenna of example 3 that may optionally include thatthe controller is operable to apply different weightings to differentbeamforming patterns when combining the separate beamforming patternsinto the first modulation pattern.

Example 9 is the antenna of example 1 that may optionally include thatthe first modulation pattern for beamforming comprises a firstmodulation pattern for holographic beamforming.

Example 10 is the antenna of example 1 that may optionally include thatthe aperture comprises a metasurface.

Example 11 is the antenna of example 10 that may optionally include thatthe metasurface comprises a single feed port to provide a feed wave tothe plurality of RF radiating antenna elements.

Example 12 is the antenna of example 10 that may optionally include thatthe metasurface comprises a plurality of feed ports to provide aplurality of feed waves to the plurality of RF radiating antennaelements simultaneously.

Example 13 is an antenna comprising: a metasurface having a single feedport to provide a feed wave, and a plurality of radio-frequency (RF)radiating antenna elements to generate, in response to the feed wave, aplurality of beams simultaneously in different directions in response toa first modulation pattern for holographic beamforming applied to theplurality of RF radiating antenna elements to establish all beams of theplurality of beams such that antenna elements of the plurality of RFradiating antenna elements contribute to all beams in the plurality ofbeams concurrently; and a controller coupled to the aperture to generatethe first modulation pattern, wherein the first modulation pattern is acombination of a plurality of modulation patterns, each modulationpattern in the plurality of modulation patterns being for a distinct oneof the plurality of beams, where the controller is operable to generateeach modulation pattern for each beam of the plurality of beams as aunique holographic beamforming pattern, combine the unique holographicbeamforming patterns for the plurality of beams into the firstmodulation pattern, and send the first modulation pattern to theaperture.

Example 14 is the antenna of example 13 that may optionally include thatthe controller is operable combine holographic beamforming patterns forthe plurality of beams into the first modulation pattern by averagingcorresponding pattern values in the plurality of modulation patterns forindividual RF radiating elements of the plurality of RF radiatingantenna elements.

Example 15 is the antenna of example 13 that may optionally include thatthe controller is operable to combine holographic beamforming patternsfor the plurality of beams into one modulation pattern by, one or moreof: averaging corresponding pattern values in the plurality ofmodulation patterns for individual RF radiating elements of theplurality of RF radiating antenna elements, and then selecting aEuclidean modulation pattern based on the one modulation pattern as thefirst modulation pattern; or calculating a plurality of Euclideanmodulation mappings for each the holographic beamforming patterns forfirst and second beams of the plurality of beams; generating a pluralityof sums by adding patterns for each of the Euclidean modulation mappingsfor first beam to patterns for each of the corresponding Euclideanmodulation mappings for the second beam, and then selecting, as thefirst modulation pattern, the Euclidean modulation pattern for theEuclidean modulation mapping having a smallest sum from the plurality ofsums; or selecting a Euclidean modulation pattern associated with aclosest Euclidean modulation mapping for each of the holographicbeamforming patterns for the plurality of beams; and averaging theEuclidean modulation patterns for the closest Euclidean modulationmappings for the plurality of the holographic beamforming patterns.

Example 16 is a method for controlling an antenna having an aperturewith a plurality of radio-frequency (RF) radiating antenna elements, themethod creating a first modulation pattern for beamforming to be appliedto the plurality of RF radiating antenna elements to generate aplurality of beams simultaneously in different directions with antennaelements of the plurality of RF radiating antenna elements contributingto all beams in the plurality of beams concurrently; and sending thefirst modulation pattern to the aperture to cause the plurality of RFradiating antenna elements to generate a plurality of beamssimultaneously.

Example 17 is the method of example 16 that may optionally include thatthe first modulation pattern is a combination of a plurality ofmodulation patterns, each modulation pattern in the plurality ofmodulation patterns being for a distinct one of the plurality of beams.

Example 18 is the method of example 17 that may optionally includegenerating each modulation pattern for each beam of the plurality ofbeams as a unique holographic beamforming pattern and combining theunique holographic beamforming patterns for the plurality of beams intothe first modulation pattern.

Example 19 is the method of example 16 that may optionally include thatcombining holographic beamforming patterns for the plurality of beamsinto the first modulation pattern comprises averaging correspondingpattern values in the plurality of modulation patterns for individual RFradiating elements of the plurality of RF radiating antenna elements.

Example 20 is the method of example 16 that may optionally include thatcombining the unique holographic beamforming patterns into the firstmodulation pattern comprises applying different weightings to differentholographic beamforming patterns when combining the unique holographicbeamforming patterns into the first modulation pattern.

Some portions of the detailed descriptions above are presented in termsof algorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the following discussion,it is appreciated that throughout the description, discussions utilizingterms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

The present invention also relates to apparatus for performing theoperations herein. This apparatus may be specially constructed for therequired purposes, or it may comprise a general-purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a computerreadable storage medium, such as, but is not limited to, any type ofdisk including floppy disks, optical disks, CD-ROMs, andmagnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any typeof media suitable for storing electronic instructions, and each coupledto a computer system bus.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.In addition, the present invention is not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the invention as described herein.

A machine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes read onlymemory (“ROM”); random access memory (“RAM”); magnetic disk storagemedia; optical storage media; flash memory devices; etc.

Whereas many alterations and modifications of the present invention willno doubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that anyparticular embodiment shown and described by way of illustration is inno way intended to be considered limiting. Therefore, references todetails of various embodiments are not intended to limit the scope ofthe claims which in themselves recite only those features regarded asessential to the invention.

We claim:
 1. An antenna comprising: an aperture having a plurality ofradio-frequency (RF) radiating antenna elements to generate a pluralityof beams simultaneously in different directions in response to a firstmodulation pattern for beamforming applied to the plurality of RFradiating antenna elements to establish all beams of the plurality ofbeams such that antenna elements of the plurality of RF radiatingantenna elements contribute to all beams in the plurality of beamsconcurrently; and a controller coupled to the aperture to generate thefirst modulation pattern.
 2. The antenna of claim 1 wherein the firstmodulation pattern is a combination of a plurality of modulationpatterns, each modulation pattern in the plurality of modulationpatterns being for a distinct one of the plurality of beams.
 3. Theantenna of claim 2 wherein the controller is operable to generate eachmodulation pattern for each beam of the plurality of beams as a separatebeamforming pattern, combine the separate holographic beamformingpatterns for the plurality of beams into the first modulation pattern,and send the first modulation pattern to the aperture.
 4. The antenna ofclaim 3 wherein the controller is operable combine beamforming patternsfor the plurality of beams into the first modulation pattern byaveraging corresponding pattern values in the plurality of modulationpatterns for individual RF radiating elements of the plurality of RFradiating antenna elements.
 5. The antenna of claim 3 wherein thecontroller is operable to combine beamforming patterns for the pluralityof beams into one modulation pattern by: averaging corresponding patternvalues in the plurality of modulation patterns for individual RFradiating elements of the plurality of RF radiating antenna elements,and then selecting a Euclidean modulation pattern based on the onemodulation pattern as the first modulation pattern.
 6. The antenna ofclaim 3 wherein the controller is operable combine beamforming patternsfor the plurality of beams into the first modulation pattern by:calculating a plurality of Euclidean modulation mappings for each thebeamforming patterns for first and second beams of the plurality ofbeams; generating a plurality of sums by adding patterns for each of theEuclidean modulation mappings for first beam to patterns for each of thecorresponding Euclidean modulation mappings for the second beam, andthen selecting, as the first modulation pattern, the Euclideanmodulation pattern for the Euclidean modulation mapping having asmallest sum from the plurality of sums.
 7. The antenna of claim 3wherein the controller is operable combine beamforming patterns for theplurality of beams into the first modulation pattern by: selecting aEuclidean modulation pattern associated with a closest Euclideanmodulation mapping for each of the beamforming patterns for theplurality of beams; and averaging the Euclidean modulation patterns forthe closest Euclidean modulation mappings for the plurality of thebeamforming patterns.
 8. The antenna of claim 3 wherein the controlleris operable to apply different weightings to different beamformingpatterns when combining the separate beamforming patterns into the firstmodulation pattern.
 9. The antenna of claim 1 wherein the firstmodulation pattern for beamforming comprises a first modulation patternfor holographic beamforming.
 10. The antenna of claim 1 wherein theaperture comprises a metasurface.
 11. The antenna of claim 10 whereinthe metasurface comprises a single feed port to provide a feed wave tothe plurality of RF radiating antenna elements.
 12. The antenna of claim10 wherein the metasurface comprises a plurality of feed ports toprovide a plurality of feed waves to the plurality of RF radiatingantenna elements simultaneously.
 13. An antenna comprising: ametasurface having a single feed port to provide a feed wave, and aplurality of radio-frequency (RF) radiating antenna elements togenerate, in response to the feed wave, a plurality of beamssimultaneously in different directions in response to a first modulationpattern for holographic beamforming applied to the plurality of RFradiating antenna elements to establish all beams of the plurality ofbeams such that antenna elements of the plurality of RF radiatingantenna elements contribute to all beams in the plurality of beamsconcurrently; and a controller coupled to the aperture to generate thefirst modulation pattern, wherein the first modulation pattern is acombination of a plurality of modulation patterns, each modulationpattern in the plurality of modulation patterns being for a distinct oneof the plurality of beams, the controller being operable to generateeach modulation pattern for each beam of the plurality of beams as aunique holographic beamforming pattern, combine the unique holographicbeamforming patterns for the plurality of beams into the firstmodulation pattern, and send the first modulation pattern to theaperture.
 14. The antenna of claim 13 wherein the controller is operablecombine holographic beamforming patterns for the plurality of beams intothe first modulation pattern by averaging corresponding pattern valuesin the plurality of modulation patterns for individual RF radiatingelements of the plurality of RF radiating antenna elements.
 15. Theantenna of claim 13 wherein the controller is operable to combineholographic beamforming patterns for the plurality of beams into onemodulation pattern by, one or more of: averaging corresponding patternvalues in the plurality of modulation patterns for individual RFradiating elements of the plurality of RF radiating antenna elements,and then selecting a Euclidean modulation pattern based on the onemodulation pattern as the first modulation pattern; or calculating aplurality of Euclidean modulation mappings for each the holographicbeamforming patterns for first and second beams of the plurality ofbeams; generating a plurality of sums by adding patterns for each of theEuclidean modulation mappings for first beam to patterns for each of thecorresponding Euclidean modulation mappings for the second beam, andthen selecting, as the first modulation pattern, the Euclideanmodulation pattern for the Euclidean modulation mapping having asmallest sum from the plurality of sums; or selecting a Euclideanmodulation pattern associated with a closest Euclidean modulationmapping for each of the holographic beamforming patterns for theplurality of beams; and averaging the Euclidean modulation patterns forthe closest Euclidean modulation mappings for the plurality of theholographic beamforming patterns.
 16. A method for controlling anantenna having an aperture with a plurality of radio-frequency (RF)radiating antenna elements, the method creating a first modulationpattern for beamforming to be applied to the plurality of RF radiatingantenna elements to generate a plurality of beams simultaneously indifferent directions with antenna elements of the plurality of RFradiating antenna elements contributing to all beams in the plurality ofbeams concurrently; and sending the first modulation pattern to theaperture to cause the plurality of RF radiating antenna elements togenerate a plurality of beams simultaneously.
 17. The method of claim 16wherein the first modulation pattern is a combination of a plurality ofmodulation patterns, each modulation pattern in the plurality ofmodulation patterns being for a distinct one of the plurality of beams.18. The method of claim 17 further comprising generating each modulationpattern for each beam of the plurality of beams as a unique holographicbeamforming pattern and combining the unique holographic beamformingpatterns for the plurality of beams into the first modulation pattern.19. The method of claim 16 wherein combining holographic beamformingpatterns for the plurality of beams into the first modulation patterncomprises averaging corresponding pattern values in the plurality ofmodulation patterns for individual RF radiating elements of theplurality of RF radiating antenna elements.
 20. The method of claim 16wherein combining the unique holographic beamforming patterns into thefirst modulation pattern comprises applying different weightings todifferent holographic beamforming patterns when combining the uniqueholographic beamforming patterns into the first modulation pattern.